The present invention relates to a dental diamond bar having electrodeposited thereon diamond abrasive grains and a manufacturing method suitable for the diamond bar.
A conventional diamond bar employed in dental treatment comprises a bar body having a rearward end portion formed into a shank portion. Diamond abrasive grains are fixedly bonded to, i.e., electrodeposited on a peripheral surface of a forward end portion of the bar body by a plating layer of metal such as nickel or the like, to form a grinding section. An annular groove is formed at an axially intermediate section of the shank portion. Colored paint is applied to the annular groove. The color of the applied paint enables a user to identify the type or kind of the diamond bar, that is, configuration of the grinding section, grain size of the abrasive grains and the like.
In the above-described diamond bar, however, since the identifying colored paint is applied to the axially intermediate section of the shank portion, it is not easy to ascertain the type or kind of the diamond bar. The reason for this is that once the shank portion of the diamond bar is fitted into a handpiece, the paint is concealed by the handpiece and cannot be seen. Also when the shank portions of the respective diamond bars are inserted respectively into a plurality of bores formed in a storage bar stand to store the diamond bars, the paints on the respective shank portions are concealed by the stand and cannot be seen. Further, it is required to form the annular groove in the shank portion in order for the paint thereon not to interfere with insertion of the shank portion into the handpiece. This correspondingly increases the manufacturing cost of the diamond bar.
The diamond bar constructed as described above is manufactured in the following manner. That is, a bar body is first prepared which comprises a shank portion having an axial intermediate section formed therein with an annular groove. The bar body further comprises a grinding-section scheduled part which extends from the shank portion to the forward end of the bar body. Subsequently, an electrically insulating material is applied to a part of the bar body which extends from the grinding-section scheduled part toward the rearward end of the bar body, to form a masking section. Then, a forward end portion of the bar body including the grinding-section scheduled part is driven into a multiplicity of diamond grains immersed in electrolytic solution containing nickel ions, to electrodeposit the diamond grains onto the grinding-section scheduled part, whereby the grinding section is formed. Since the diamond grains are not electrodeposited on the masking section of the bar body, the rearward edge of the grinding section is brought into conformity with the forward edge of the masking section. Subsequently, the masking section is removed, and then colored paint is applied to the annular groove. Thus, the dental diamond bar is obtained as a final product.
Japanese Patent Application Laid-Open No. 62-49845 has been filed by the same assignee as that of the present invention and has been laid open to public inspection on Mar. 4, 1987. The Japanese patent discloses a technique of the above-mentioned masking in which bar bodies are dipped into masking liquid to form masking sections on the respective bar bodies. The masking technique is superior in operability. However, the forward edge of the masking section is often unstable in position, so that the rearward edge of the grinding section might not be constant in position, or might wave or undulate when the bar body is viewed in side elevation. This would result in a variation in length of the grinding section from product to product, and a variation in configuration of the rearward edge of the grinding section from product to product.
The above-mentioned Japanese patent describes, as the prior art, a technique of applying masking liquid to a bar body by means of a brush to form a masking section on the bar body. It is possible for such masking technique to correctly determine the forward edge of the masking section, so that the position of the rearward edge of the grinding section can be made constant. Thus, the rearward edge of the grinding section can be made straight when the bar body is viewed in side elevation. However, the masking technique is extremely low in operating efficiency, because the masking is effected manually.
The above-mentioned Japanese patent also describes, as the prior art, a masking technique in which an insulating tape is wrapped about a bar body. Such masking technique has advantages and disadvantages similar to those of the above-described masking technique in which the masking liquid is applied to the bar body by means of a brush.